Security mechanism for computer processing

ABSTRACT

To provide improved security in adjunct program modules such as plug-ins and dynamic link libraries, a requesting module provides an authorization interface to the invoked module such that the invoked module can require a certificate of the requesting module and can also challenge the authority of the requesting module. The certificate can include one or more permissions which are prerequisites for processing by the invoked module. The invoked module can challenge the authority of the requesting module by sending random test data to the requesting module and receiving in response a cryptographic signature of the test data. By verifying the signature of the requesting module using the received certificate, the invoked module confirms that the requesting module is, in fact, the owner of the receive certificate.

REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 11/107,103, filed Apr.14, 2005, which is a continuation of application Ser. No. 09/773,256,filed Jan. 30, 2001.

BACKGROUND OF THE INVENTION

Computer programs are currently made extensible and efficient by the useof adjunct program modules such as plug-ins and dynamic link libraries.Plug-ins are computer program modules which can alter the behavior of acomputer program without changing the computer program itself. A commonexample of plug-ins are those associated with currently ubiquitous webbrowsers. Briefly, a web browser is a computer program by which a userretrieves multimedia documents and information through that portion ofthe Internet known as the World Wide Web. Installation of plug ins allowmodification of the behavior of the web browser without re-installing orotherwise changing the computer instructions of the web browser itself.One example of such extended functionality is the embedded display ofimages of the Tagged Image File Format (TIFF). Such functionality is notprovided by some web browsers currently, but installation of certainplug-ins add that functionality. To use the plug-in, applications suchas web browsers are designed to look for installed plug-ins and, ifinstalled, invoke execution of those plug-ins upon activation of aparticular function or activity.

Plug-ins can sometimes be implemented as dynamic link libraries. Dynamiclink libraries can be used for other purposes as well. A dynamic linklibrary is a collection of program modules which are generally notloaded until invoked by another program. The following example willillustrate. Consider a web browser which provides a spell-checkingcapability for forms data entry. A web browser is typically aresource-intensive program such that a considerable amount of memory isused when the web browser is executing A spell-checker can also beresource-intensive. By implementing the spell-checker as part of adynamic link library, execution of the web browser does not immediatelyload the spell-checker into memory. Accordingly, the resources requiredfor the spell-checker are not immediately consumed. Instead, thespell-checker is loaded for execution only when a user requests a spellchecking function of the web browser. Such allows the web browser toexecute more efficiently when the spell-check function is not invoked.

For reasons pertaining both to extensibility and efficiency, adjunctprogram modules such as plug-ins and modules of dynamic link librariesare quite popular. An additional factor in the popularity of suchadjunct program modules is the simplicity with which they areimplemented. To facilitate the use of adjunct processing modules, suchmodules are designed to be very easily identified and invoked. Virtuallyno safeguards are used to ensure only a specifically authorized computerprogram invokes execution of a particular adjunct program module.

The lack of security in adjunct program modules is a significantproblem. The following example is illustrative. Consider that a computeruser has collected a number of musical songs in the ubiquitous andrenowned MP3 digital format and plays the songs on a computer using anMP3 player program. Consider further that the user has purchased anddownloaded a number of songs in a secure, copy-protected format butwishes to play those songs along with the other songs in the MP3 format.The MP3 player program can be augmented with a plug-in adjunct programmodule to decode and play the secure, copy-protected format. Such anadjunct program module, when requested, can decode the secure,copy-protected music and produce un-secured, un-protected music forreproduction through the computer's sound logic and loudspeakers.

However, due to the accessibility of conventional adjunct programmodules, any program could request decoding of the secure,copy-protected music data by the decoding adjunct program module.Accordingly, a cracker could write a simple program to request decodingfrom the adjunct program module and to re-write the decoded music in theMP3 format. The resulting MP3 music data file could have identical soundquality and could be distributed worldwide through the Internet withoutany encryption security or copy protection. Such would represent acatastrophic failure of the secure, copy-protected format decoded by theadjunct program module.

What is therefore needed is a security mechanism by which adjunctprogram modules can limit service to authorized program modules. Suchwould enable security-reliant computer processes to avail themselves ofthe benefits and advantages of adjunct program modules.

SUMMARY OF THE INVENTION

In accordance with the present invention an adjunct program module canrequire a certificate from a requesting program module to authenticatethe requesting program module as authorized to request processing by theadjunct program module. The adjunct program module only performsrequested processing when the certificate received from the requestingprogram module indicates that the requesting program module isauthorized to request such processing. In this way, processing is notperformed when requested by an unauthorized program module and securityis significantly enhanced.

The interface of the adjunct program module indicates that the adjunctprogram module requires an authorization interface of the requestingprogram module. The authorization interfaces specifies the manner inwhich the invoked adjunct program module can request authorization. Theuse of an authorization interface allows increased flexibility in theimplementation of authorization protocols according to the presentinvention. If the invoked adjunct program module requires a certificatefor authentication, the invoked adjunct program module requests, andreceives, the certificate from the requester using the requester'sauthorization interface.

There are a number of ways in which the certificate can be validated asindicating that the requesting program module is authorized to requestsuch processing. The certificate is cryptographically signed by acertificate authority and verification of that signature ensures that noentity has tampered with the certificate, perhaps to alter the identityof the owner of the certificate or to add permissions to thecertificate. Failure to validate the certificate authority's signatureresults in refusal to perform the requested processing.

The received certificate only authorizes processing by the owner of thecertificate. The received certificate identifies its owner. If theprogram module requesting processing is not the owner of thecertificate, the adjunct program module refuses to perform the requestedprocessing. The owner's identity can be verified using achallenge-response protocol. In addition, the certificate expires at apredetermined time, and the adjunct program module refuses to performthe requested processing if the certificate has expired.

The certificate also includes a number of permissions. Each permissionincludes data which is associated with one or more types of actionswhich are authorized by the certificate. The adjunct program module canbe configured to perform processing only when the received certificateincludes a specific, predetermined permission. The use of permissionsadds a significant degree of flexibility in the security protocoldescribed herein. For example, a particular permission could grant itsowner the authority to examine parts of a secure, copy-protected audiosignal, such as the title and artist of the audio signal, withoutgranting authority to the decoded, unsecured, unprotected audio datastream.

As mentioned above, the identity of the requester as the owner of thecertificate can be challenged. Thus, stealing a certificate of, andmasquerading as, an authorized requesting program module isinsufficient. The challenge response mechanism according to the presentinvention verifies that the requesting module has access to a privatekey associated with the certificate.

To challenge the authority of the requesting module, the adjunct programmodule randomly produces test data and requires that the requestercryptographically processes the test data as a precondition toperforming processing requested by the requester. The cryptographicprocessing by the requester involves asymmetric key encryption and useby the requester of the requester's private key. Requiring cryptographicuse of the requester's private key establishes that the private key ofthe requester matches the public key of the requester's certificate andtherefore confirms the requester's identity and authority.

Individually, each of these individual security mechanisms can be usedby the adjunct program module to significantly deter unauthorized use ofadjunct program modules. The described security mechanisms can also becombined to provide a tremendous deterrence to unauthorized use ofadjunct program modules over conventional adjunct program moduleinterfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an application and two program moduleswhich use certificates to authorize processing in accordance with thepresent invention.

FIG. 2 is a block diagram of a computer system in which the applicationand adjunct program modules of FIG. 1 execute.

FIG. 3 is a block diagram of a certificate of FIG. 1 in greater detail.

FIG. 4 is a logic flow diagram of a secure adjunct program interface inaccordance with the present invention.

FIG. 5 is a logic flow diagram of the certificate verification of FIG. 4in greater detail.

FIGS. 6A-B are a logic flow diagrams of respective embodiments of achallenge response authentication interface in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, a security protocol isimplemented between an application 102 (FIG. 1) and a component 104A andbetween component 104A and a component 104B. Components 104A-B areadjunct program modules which are loaded and executed separately fromapplication 102 and from each other but execution of which can berequested for application 102 or other components. In this illustrativeembodiment, components 104A-B are modules of one or more dynamic linklibraries (DLLs). The very nature of adjunct program modules suggeststhat execution of adjunct program modules by other program modules isboth easy and straight-forward. However, because of security protocolsdescribed herein, adjunct program modules can be used to perform tasksin which security is required.

Application 102 and components 104A-B are each all or part of one ormore computer processes executing within computer system 200 (FIG. 2).Computer system 200 includes one or more processors 202 and a memory 204which can include randomly accessible memory (RAM) and read-only memory(ROM) and can include generally any storage medium such as magneticand/or optical disks. Memory 204 and processors 202 interact with oneanother through an interconnect 206.

A user interacts with computer system 200 through one or moreinput/output (I/O) devices 208 which can include, for example, akeyboard, an electronic mouse, trackball, tablet or similar locatordevice, an optical scanner, a printer, a CRT or LCD monitor, a soundcard, a microphone, one or more loudspeakers, and/or a network accessdevice through which computer system 200 can be connected to a computernetwork. To facilitate understanding of the inter-operation of theelements of computer system 200 according to this illustrativeembodiment, the illustrative example of playback of secured andcopy-protected audio data is continued. Under control of a user, e.g.,through physical manipulation of one or more of I/O devices 208,application 102 and components 104 collectively decode the secured,copy-protected audio data to produce raw audio data for playback throughone or more of I/O devices 208 such as a sound card and loudspeakers.While computer system 200 is shown to be a single computer system, it isappreciated that application 102 and/or one or more of components 104can be distributed over multiple computer systems which areinterconnected to perform the functions described herein.

Furthering the illustrative example of decoding and playing backsecured, copy-protected audio data, such decoding is performed by one ofcomponents 104, e.g., component 104B (FIG. 1). To accomplish suchdecoding, application 102 requests execution of component 104A which inturn requests execution of component 104B. In this illustrative example,component 104A verifies authorization of the user to access the securedaudio data prior to requesting decoding of the secured audio data bycomponent 104B. Since component 104B decodes secured audio data andreturns the raw audio data in this illustrative example, it is desirablethat component 104B ensures that such decoding is performed only forduty authorized requesters, e.g., component 104A and/or application 102.

As shown in FIG. 1, component 104B includes substantive computer code144B which, in this illustrative example, decodes secured,copy-protected audio data and produces raw audio data when executed.Substantive computer code 144B includes computer instructions and datawhich collectively specify the behavior of component 104B. Component104A includes substantive computer code 144A which is analogous tosubstantive computer code 144B of component 104B. Substantive computercode 124 of application 102 is also analogous to substantive computercode 144A-B. Of course, substantive computer code 124 and 144A canspecify a different behavior than that specified by substantive computercode 144B.

Application 102 includes interface references 120, each of whichidentifies an interface which in turn specifies a manner in whichapplication 102 interacts with an adjunct program module such ascomponent 104A. Component 104A includes an invocation interface 145Awhich specifies a manner in which execution of component 104A isinvoked. To request processing by component 104A, application 102 mustfirst acquire access to invocation interface 145A. Application 102requests, and component 104A provides, a reference to invocationinterface 145A which application 102 stores in interface references 120and subsequently uses to request processing from component 104A.

Component 104A also includes one or more interface references 140A eachof which identifies an interface which in turn specifies a manner bywhich component 104A can invoke execution of other components such ascomponent 104B. Component 104B includes invocation interface 145B andinterface references 140B which are analogous to invocation interface145A and interfaces 140A, respectively, of component 104A.

To facilitate the security protocol described herein, each applicationand component can include an authorization interface. For example,application 102 includes authorization interface 129 which specifies themanner in which another program module can request authentication ofapplication 102. Components 104A-B similarly include authorizationinterfaces 149A-B, respectively.

Application 102 also includes an authorization provider 128 whichincludes computer instructions and data which specify the behavior ofapplication 102 when authentication is requested in accordance withauthorization interface 129. Components 104A and 104B similarly includeauthorization providers 148A and 148B, respectively.

To authenticate a requesting program module, an adjunct program modulecan request a certificate of the requesting program module. In response,the authorization provider of the requesting program module supplies acertificate of the requesting program module. For example, application102 includes a certificate 122, component 104A includes a certificate142A, and component 104B includes a certificate 142B. While eachcertificate is shown to be included within each application orcomponent, each certificate can alternatively be stored in memory 204(FIG. 2) separately from the associated application or component of thecertificate. For example, certificate 122 can be stored within memory204 separately from application 102. Such facilitates replacement ofexpired certificates or replacement of a certificate with another, e.g.,to change the permissions of the certificate.

Certificates are well-known and are described herein for completeness.However, full appreciation of certificates requires a basicunderstanding of asymmetric encryption which is also well-known andwhich is also described herein for completeness. The simplest ofencryption techniques uses the same key for encryption and decryption.Encryption scrambles data from its original, native form to a scrambled,apparently undecipherable form. Decryption recovers the original datafrom the scrambled, apparently undecipherable form. Symmetric keyencryption can be satisfactory for secure archival in which the personwho is likely to want to decrypt the data is the same person whoencrypted the data in the first place. However, when one party wishes toencrypt data for secure transport to another party, symmetric keyencryption requires that the key is somehow transported as well,compromising security and/or representing a significant inconvenience.

Asymmetric key encryption uses pairs of reciprocal keys. The keys arereciprocal in that encryption by one key of the pair can only be undoneby decrypting using the other key of the pair. Asymmetric key encryptionis sometimes referred to as public key encryption because one key of apair of reciprocal keys is held in strict secrecy and privacy while theother key of the pair is distributed publicly within the system ofintended use of the public key. The system of intended use can be aslarge or larger than the Internet and can be as-small as a singlecomputer. Data can be encrypted for transport to a receiving party byencrypting the data using the public key of the receiving party. Thus,only the private key of the receiving party can decrypt the data.

Public key encryption also permits cryptographic signatures of data. Tosign a collection of data, a parry uses its private key to encrypt thedata or, alternatively, to form a hash of the data such that the data isstill available in cleartext form without verification of the signature.The data can be decrypted—or alternatively the hash can beverified—using the public key of that party. Since the public key iswidely and publicly distributed within the system of intended use, thedata is not secure when encrypted in this manner. However, successfuldecryption of the data using the party's public key verifies that it wasencrypted by the party using its private key and therefore verifies theauthenticity of the data as originating with the signing party. Such acryptographic signature can be used to verify that no one has tamperedwith the data after the data was cryptographically signed.

One issue with verifying cryptographic signatures is verification that aparticular public key belongs to a particular party. For example, acryptographic signature from a trusted party is only as reliable as thecertainty that the public key used to verify the signature is truly fromthe trusted party and not some imposter. A certificate binds a publickey to a particular party. Generally, a certificate includes a publickey and data identifying the owner of the public key. The certificate issigned by a trusted certificate authority which is typically anorganization that is widely trusted to issue certificates. Thecryptographic signature of the certificate authority ensures that no onehas tampered with the certificate after its issuance.

Certificate 122 (FIG. 1) is shown in greater detail in FIG. 3 and isillustrative. Certificates 142A-B (FIG. 1) are analogous to certificate122 and the following description of certificate 122 in the context ofFIG. 3 is equally applicable to certificates 142A-B.

Certificate 122 (FIG. 3) includes a public key 302 and an owner field304. Owner field 304 stores data identifying application 102 (FIG. 1) asthe owner of certificate 122. Public key 302 (FIG. 3) is a public key ofapplication 102 (FIG. 1). Certificate authority field 306 (FIG. 3)stores data identifying the certificate authority which issuedcertificate 122. Expiration field 308 stores data specifying a timeafter which certificate 122 is no longer valid.

Certificate 122 includes a number of permissions 310. Each ofpermissions 310 includes data specifying one or more types of actionswhich are permitted for the owner of certificate 122, e.g., application102 (FIG. 1). Permissions 310 are used in a manner described morecompletely below to limit the types of actions adjunct program modulescan perform at the request of application 102. Certificate 122 iscryptographically signed by the certificate authority to preventtampering.

Logic flow diagrams 400A-B (FIG. 4) illustrate an adjunct program moduleinterface with enhanced security in accordance with the presentinvention. Logic flow diagram 400A illustrates processing by arequesting application or a requesting adjunct program module, and logicflow diagram 400B illustrates processing by an invoked adjunct programmodule. In particular, an invoked adjunct program module, e.g.,component 104B, includes an authorization verifier, e.g., authorizationverifier 147B, which verifies authority of the requesting program moduleprior to performing the requested processing. In the context of logicflow diagrams 400A-B, the requesting application or adjunct programmodule is sometimes referred to as the requester. In the illustrativeexample of FIG. 1, the requester can be application 102 and the invokedadjunct program module can be component 104A. Alternatively, therequester can be component 104A and the invoked adjunct program modulecan be component 104B.

In step 402 (FIG. 4), the requester invokes the invoked adjunct programmodule in a conventional manner sending a number of parameters and anauthorization interface. The parameters required by the invoked adjunctprogram module are specified by the invocation interface of the invokedadjunct program module. In this illustrative example, component 104B(FIG. 1) is the invoked adjunct program module and invocation interface145B specifies the parameters required for proper execution ofsubstantive computer code 144B. Each such required parameter is data tobe supplied by the requester, e.g., component 104A in this illustrativeexample.

The required parameters can include the authorization interface of therequester, e.g., authorization interface 149A. The required parameterscan also, or alternatively, require an authorization interface of arequester of the requester. In this illustrative example, invocationinterface 145B can require the authorization interface of application102, e.g., authorization interface 129, in lieu of or in addition to theauthorization interface of the requester, e.g., authorization interface149A of component 104A.

In step 452, component 104B (FIG. 1) receives the parameters andauthorization interface. In step 454, authorization verifier 147B(FIG. 1) of component 104B requests and receives the certificate of therequester, e.g., certificate 142A, using the received authorizationinterface. In step 404, the authorization provider of the requester,e.g., authorization provider 148A, receives the request for thecertificate and sends the certificate.

In test step 456 (FIG. 4), authorization verifier 147B (FIG. 1)determines whether the certificate authorizes processing in a mannerdescribed more completely below. If so, component 104B proceeds withprocessing according to substantive computer code 144B in step 458 (FIG.4). Conversely, if the certificate does not authorize processing,component 104B produces an error message as the results of processing instep 460. In step 462, component 104B sends the results, either fromstep 458 or from step 460, to the requester. In step 406, the requesterreceives the results from the invoked adjunct program module.

As described above, authorization verifier 147B verifies that thereceived certificate authorizes processing in test step 456. Test step456 is shown in greater detail as logic flow diagram 456 (FIG. 5). Instep 502, authorization verifier 147B (FIG. 1) verifies the signature ofthe certificate authority of the received certificate. In thisillustrative example, the certificate received by authorization verifier147B in step 454 (FIG. 4) is certificate 122 (FIGS. 1 and 3). In otherexamples, the received certificate can be certificate 142A (FIG. 1) oranother certificate.

The certificate authority of certificate 122 (FIG. 3) is identified bycertificate authority field 306. To verify the signature of certificate122, authorization verifier 147B (FIG. 1) uses a certificate authoritypublic key 141B. Since the public key is widely and publicly distributedwithin the system of intended use, application 102 and components 104A-Ball include copies of the public key of the certificate authority orotherwise have access to a copy. In test step 504 (FIG. 5),authorization verifier 147B determines whether the signature of thecertificate authority is verified. If so, processing transfers to teststep 506.

In test step 506, authorization verifier 147B (FIG. 1) determineswhether certificate 122 has expired by reference to a date and timerepresented by expiration field 308 (FIG. 3). If the certificate has notexpired, processing transfers to step 508.

In step 508, authorization verifier 147B challenges the requester toverify the identity of the requester. As described above, the requestercan have directly or indirectly requested processing by component 104B.The manner in which the requester is challenged and responds isdescribed more completely below. In test step 510, authorizationverifier 147B determines whether the requester responded properly to thechallenge. If so, processing transfers to test step 512.

In test step 512, authorization verifier 147B determines whether thecertificate in question includes one or more required permissions. Inparticular, component 104B performs processing only when a certificategrants the direct or indirect requester permission for such processing.Thus, component 104B is configured to perform requested processing onlywhen a supplied certificate includes one or more requisite permissions.Accordingly, authorization verifier 147B of component 104B, in test step512, searches permissions 310 (FIG. 3) for the one or more requisitepermissions.

If all requisite permissions are found in the supplied certificate,processing transfers to terminal step 514 in which authorizationverifier 147B of component 104B determines that the supplied certificateauthorizes processing at the request of the requester. Conversely, if(i) one or more requisite permissions are not found in the suppliedcertificate (test step 512) or (ii) the requester responds improperly tothe challenge (test step 510) or (iii) the supplied certificate hasexpired (test step 506) or (iv) the certificate's signature by thecertificate authority is not verified (test step 504), processingtransfers to terminal step 516 in which authorization verifier 147B ofcomponent 104B determines that the supplied certificate does notauthorize processing at the request of the requester.

Thus, an attempt to request processing by component 104B from anunauthorized program module is prevented. Consider for example thatcomponent 104B decoded secure and copy-protected audio data for playbackand produced therefrom uncompressed, cleartext, digital audio signals.Component 104B can require authentication of both component 104A as adirect requester and application 102 as an indirect requester. Any othermodule attempting to use component 104B to decode and decrypt such audiosignals would have to produce a certificate identifying itself, havingthe proper permissions (test step 512), and signed by a certificateauthority (test step 504). In addition, the imposter module would haveto correctly respond to a challenge of the imposter's authority in steps508-510. Each of these mechanisms provides security well beyond anysecurity provided by conventional adjunct program modules.

The challenge-response authentication of steps 508-510 is shown morecompletely as logic flow diagram 508 (FIG. 6A) and processing by therequester in response to the challenge is illustrated by logic flowdiagram 600. An alternative embodiment of step 508 is shown as logicflow diagram 508B (FIG. 6B) and is described more completely below.

Processing according to logic flow diagram 508 (FIG. 6A) begins withstep 602 in which authorization verifier 147B of component 104Bgenerates random or pseudo-random data. In step 604 (FIG. 6A),authorization verifier 147B (FIG. 1) sends the random data to therequester associated with the certificate in question. As describedabove, the requester can be a direct requester such as component 104A oran indirect requester such as application 102. In this illustrativeexample, the challenged requester is component 104A.

Component 104A includes challenge code 143A which includes computerinstructions and data which collectively specify a behavior ofauthorization provider 148A of component 104A in response to a challengesuch as that initiated by component 104B in step 604 (FIG. 6A).Processing in accordance with challenge code 143A is illustrated bylogic flow diagram 600. In step 652, authorization provider 148Areceives the random data. In step 654, authorization provider 148Acryptographically signs the random data using private key 146A (FIG. 1).Private key 146A is the reciprocal key to the public key included incertificate 142A. In step 656, authorization provider 148A sends thesigned random data, or alternatively a hash signature of the randomdata, to component 104B as the response to the challenge.

In step 606, authorization verifier 147B receives the decrypted randomdata. In test step 608, authorization verifier 147B verifies thesignature of the random data using the public key of the certificate inquestion. If the received signature is verified, authorization verifier147B establishes that the requester responded properly to the challenge,thus proving that the requester has the private key associated with thesupplied certificate. Conversely, if the received signature is notverified, authorization verifier 147B establishes that the requester didnot respond properly to the challenge and therefore may not have theassociated private key. Thus, as a precondition for processing asrequested, component 104B can require both authentication in the form ofa certificate and evidence that the requester has the associated privatekey in the requester's possession. Such represents a high level ofsecurity against unauthorized requests for processing by adjunct programmodules.

An alternative challenge-response protocol is shown in logic flowdiagrams 600B (FIG. 6B) and 508B in which processing begins with step622. In step 622, authorization verifier 147B generates random orpseudo-random data. In step 624, authorization verifier 147B encryptsthe random data using the public key of the certificate. In step 626,authorization verifier 147B (FIG. 1) sends the encrypted random data tothe requester associated with the certificate in question.

In step 672, authorization provider 148A (FIG. 1) receives the encryptedrandom data. In step 674 (FIG. 6B), authorization provider 148A (FIG. 1)decrypts the encrypted random data using private key 146A. Successfuldecryption of the encrypted random data establishes possession ofprivate key 146A and therefore establishes proper ownership ofcertificate 142A received by component 104B. In step 676 (FIG. 6B),authorization provider 148A (FIG. 1) sends the decrypted random data tocomponent 104B as the response to the challenge.

In step 628 (FIG. 6B), authorization verifier 147B (FIG. 1) receives thedecrypted random data. In test step 610, component 104B compares thereceived decrypted random data with the original random data. If thereceived decrypted random data matches the original random data,component 104B establishes that the requester responded properly to thechallenge. Conversely, if the received decrypted random data isdifferent from the original random data, component 104B establishes thatthe requester did not respond properly to the challenge.

A number of advantages are realized by interposing an authorizationinterface between the invoked adjunct program module and the requestingprogram module. One such advantage is a significant degree offlexibility in implementing the security protocol described herein. Thefollowing example is illustrative. Consider that application 102 invokescomponent 104B directly and that later component 104A is interposedbetween application 102 and component 104B. Such is possible with verylittle modification, if any, to application and component 104B.Component 104B can still require certificate 122 of application 102 andcan require proper challenge-response from application 102.

Specifically, application 102 invokes component 104A and providesauthorization interface 129. Component 104A subsequently invokescomponent 104B and provides authorization interface 149A. Withoutmodification, authorization verifier 147B expects to receive certificate122 of application 102 and preconditions proper response to a challengeby application 102 in the manner described above. Accordingly,authorization verifier 147B requests a certificate using authorizationinterface 149A.

Authorization provider 148A receives the request for a certificate.However, since component 104B is constructed with the knowledge thatcomponent 104B expects to interact directly with application 102,authorization provider 148A requests and receives certificate 122 fromapplication 102 using authorization interface 129 and passes certificate122 to authorization verifier 147B. Accordingly, authorization verifier147B receives the expected certificate.

Similarly, authorization provider 148A can forward authority challengesfrom authorization verifier 147B to authorization provider 128 and canforward associated responses from authorization provider 128 toauthorization verifier 147B and thus preserve the authenticationverification between application 102 and component 104B.

The flexibility afforded by the use of authorization protocols enablescountless other possibilities. For example, authorization provider 148Acan require authority verification by authorization verifier 147A andauthorization provider 128 as a prerequisite to providing a requiredcertificate to authorization verifier 147B. In addition, authorizationprovider 148A can include multiple certificates, each with differentpermissions and can provide a specific one of the certificates dependingupon various circumstances.

Another advantage of using authorization interfaces is that the behaviorof an authorization provider can be subsequently modified withoutrequiring modification of other elements of a particular program module.

Yet another advantage of using authorization interfaces is thatauthorization code can be supplied separately from the substantivecomputer code of a particular program module. For example, one entitycan provide authorization provider 148A and authorization interface 149Aas object code to be linked into component 104A by a second, separateentity. Thus, the first-mentioned entity can provide the public keyinfrastructure of authorization provider 148A without disclosing thespecific details of the public key infrastructure, thus preserving thesecurity provided by the public key infrastructure. Simultaneously, thesecond entity can construct authorization verifier 147A to requestcertificates and challenge authorization of requesting program modulesusing authorization interfaces of those program modules withoutrequiring knowledge of the specific details of the public keyinfrastructure. Such allows the security protocol described hereinwithout disclosing the specific details to those who use the securityprotocol.

The above description is illustrative only and is not limiting. Instead,the present invention is defined solely by the following claims.

1. A method for authorizing requested processing by an adjunct programmodule, the method comprising: receiving a request from a requestermodule wherein the request includes at least one parameter specified byan invocation interface of the adjunct program module and the at leastone parameter includes at least an authorization interface of arequester module, the authorization interface specifying a manner inwhich a program module can request authentication; requesting acertificate of the requester module using the authorization interface ofthe requester; receiving a certificate of the requester module using theauthorization interface of the requester; requesting authentication fromthe requester module by submitting authority challenges using theauthorization interface, wherein the authority challenges are designedto establish that at least one of the requester module and a priorrequester module has possession of a private key associated with thereceived certificate; receiving responses to the requestingauthorization; determining whether the responses authorize processing inresponse to the request; if the responses do not authorize processing,aborting processing; if the responses do authorize processing:determining whether permissions associated with the certificate aresatisfied; if permissions associated with the certificate are notsatisfied, aborting the processing; if the permissions are satisfied,performing the processing.
 2. The method of claim 1, wherein therequester module is not an originating requester module.
 3. The methodof claim 2, the further comprising forwarding responses to a secondadjunct program module to preserve authentication verification betweenan originating prior requestor module and the second adjunct programmodule.
 4. The method of claim 1, wherein determining whetherpermissions are not satisfied comprises: determining one or more typesof actions permitted by the permissions, wherein one or more types ofactions permitted include granting authority to examine parts of asecure, copy-protected audio signal; and determining that the one ormore types of actions includes at least one type of action associatedwith processing to be performed in response to the request.
 5. Themethod of claim 4, wherein the parts of a secure, copy-protected audiosignal include title and artist of the audio signal.
 6. The method ofclaim 1, further comprising preserving an interaction between a secondadjunct program module and an expected requesting module by uponreceiving a request from the expected requesting module, requestingprocessing by the adjunct program module.
 7. The method of claim 1,wherein the responses comprise random data signed with a private key ofthe requester.
 8. A computer-readable storage medium having storedthereon computer-executable instructions for performing stepscomprising: receiving a request from a requesting module, wherein therequesting module received the request from at least one prior requestormodule, the request originating from an originating prior requestormodule, wherein the request includes an authorization interface thatspecifies a manner in which a program module can request authentication;requesting authorization from the requesting module using the receivedauthorization interface by submitting authority challenges to therequesting module, wherein authorization is then required from the atleast one prior requestor module, including the originating priorrequestor module, the requesting module forwarding the authoritychallenges to the originating prior requestor module and forwardingassociated responses from the originating prior requestor module;receiving authorization data in response to the requestingauthorization, the authorization data comprising the responses from theoriginating prior requestor module; and determining whether theauthorization data authorizes processing in response to the request. 9.The computer readable storage medium of claim 8, wherein anauthorization provider of the at least one prior requestor modulerequires authority verification by an authorization verifier of theoriginating prior requestor module as a prerequisite to providing theauthorization data.
 10. The computer readable storage medium of claim 9,wherein an authorization provider of the originating prior requestormodule forwards associated responses to an authorization verifier of theadjunct program module to preserve authentication verification betweenthe originating prior requestor module and the adjunct program module.11. The computer readable storage medium of claim 8, wherein determiningcomprises: determining that the authorization data includes dataspecifying one or more types of actions permitted by the authorizationdata, wherein one or more types of actions permitted include grantingauthority to examine parts of a secure, copy-protected audio signal; anddetermining that the one or more types of actions includes at least onetype of action associated with processing to be performed in response tothe request.
 12. The computer readable storage medium of claim 11,wherein the parts of a secure, copy-protected audio signal include titleand artist of the audio signal.
 13. The computer readable storage mediumof claim 8, having stored thereon further computer-executableinstructions for processing the request if the authorization dataauthorizes the processing.
 14. The computer readable storage medium ofclaim 8, having stored thereon further computer-executable instructionsfor refusing to process the request if the authorization data fails toauthorize the processing.
 15. A computer system comprising: a processoroperative to execute computer executable instructions; and memory havingstored therein computer executable instructions for performing thefollowing steps: receiving a request from a requesting module, whereinthe requesting module received the request from at least one priorrequestor module, the request originating from an originating priorrequestor module, wherein the request includes an authorizationinterface that specifies a manner in which a program module can requestauthentication; requesting authorization from the requesting moduleusing the authorization interface by submitting authority challenges tothe requesting module, wherein authorization is then required from theat least one prior requestor module, including the originating priorrequestor module, the requesting module forwarding the authoritychallenges to the originating prior requestor module and forwardingassociated responses from the originating prior requestor module;receiving authorization data in response to the requestingauthorization, the authorization data comprising the responses from theoriginating prior requestor module; and determining whether theauthorization data authorizes processing in response to the request. 16.The computer system of claim 15, wherein an authorization provider ofthe at least one prior requestor module requires authority verificationby an authorization verifier of the originating prior requestor moduleas a prerequisite to providing the authorization data.
 17. The computersystem of claim 16, wherein an authorization provider of the originatingprior requestor module forwards associated responses to an authorizationverifier of the adjunct program module to preserve authenticationverification between the originating prior requestor module and theadjunct program module.
 18. The computer system of claim 15, whereindetermining comprises: determining that the authorization data includesdata specifying one or more types of actions permitted by theauthorization data, wherein one or more types of actions permittedinclude granting authority to examine parts of a secure, copy-protectedaudio signal; and determining that the one or more types of actionsincludes at least one type of action associated with processing to beperformed in response to the request.
 19. The computer system of claim18, wherein the parts of a secure, copy-protected audio signal includetitle and artist of the audio signal.
 20. The computer system of claim15, wherein the computer executable instructions are further forprocessing the request if the authorization data authorizes theprocessing.